Flow sensing dual pump switching system and method

• US 8,834,134 B2
• Filed: 12/20/2010
• Issued: 09/16/2014
• Est. Priority Date: 12/20/2010
• Status: Active Grant

• Current Assignee: Woodward Incorporated
• Original Assignee: Woodward Incorporated
• Inventors: Baker, Carthel C., Baryshnikov, Dmitriy
• Primary Examiner(s): BERTHEAUD, PETER JOHN
• Application Number:
  US12/972,905
• Publication Number:
  US 20120156061A1
• Time in Patent Office: 1,366 Days
• Field of Search: 417/2, 417/3, 417/4, 417/286, 417/288, 417/302, 417/304, 417/307, 417/308, 417/310, 417/428, 417/440, 123/446
• US Class Current: 417/288
• CPC Class Codes: F02C 7/232 Fuel valves control of fuel supply by means of fuel metering valves F02C9/263; Draining valves or systems valves in general F16K
• CPC Class Codes: F02C 7/236 Fuel delivery systems comprising two or more pumps
• CPC Class Codes: F02C 9/263 by means of fuel metering valves
• CPC Class Codes: F04B 23/04 Combinations of two or more pumps
• CPC Class Codes: F05D 2260/606 Bypassing the fluid
• CPC Class Codes: F05D 2270/3015 differential pressure

Abstract

A flow sensing dual pump switching system and method are provided that control the supply of fuel from a dual pump fuel system to a fuel metering unit. The system senses bypass pressure from the fuel metering unit to control the differential pressurization of the second pump. As the bypass is reduced, the pressure of the second pump is increased so that it may be added to that of the first pump to supply the increased fuel consumption needs of an engine. As the fuel consumption needs decrease, the flow from the second pump added to the first pump is reduced and the differential pressure of the second pump is similarly reduced. If the bypass pressure remains high, the switching system disconnects the output of the second pump from that of the first in favor of bypassing the flow to its input to reduce its differential pressure and conserve energy.

Claims

1. A switching system for use with a dual pump fuel supply system for an aircraft engine, the dual pump fuel supply system including a first pump having a first high pressure output coupled to a high pressure supply to a fuel metering unit, wherein the fuel metering unit is configured to supply a portion of the fuel supply to an engine and to return a bypass flow of the fuel supply to a low pressure return that is coupled to a first low pressure supply to the first pump, and a second pump having a second high pressure output and a second low pressure supply that is coupled to the low pressure return, the second pump also having a second pump bypass that is coupled to the second low pressure supply, comprising:

means for sensing the bypass flow coming directly from the fuel metering unit;

means, operatively coupled to the means for sensing the bypass flow coming directly from the fuel metering unit, for controlling a pressurization of the second pump; and

means for adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump, wherein said means for adding are downstream from the first and second high pressure outputs and upstream from the fuel metering unit.

2. The switching system of claim 1, wherein the means for sensing the bypass flow from the fuel metering unit includes a sensing valve having a sensing port coupled to a bypass return from the fuel metering unit, a return port coupled to the low pressure return, and a sensing valve valving member positioned therebetween, the sensing valve further including a position port, a pressure reduction port, and a pressure addition port, wherein a differential pressure between the sensing port and the return port controls a position of the sensing valve valving member, and wherein the position of the sensing valve valving member selectively couples one of the pressure reduction port or the pressure addition port to the position port.

3. The switching system of claim 2, wherein the means for adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump includes a flow sharing valve having a first port coupled to the second high pressure output of the second pump, an adder port coupled to high pressure supply to the fuel metering unit, a third port coupled to the position port of the sensing valve, a flow sharing valve return port coupled to the low pressure return, and a flow sharing valve valving member, and wherein a differential pressure between the flow sharing valve return port and the third port controls a position of the flow sharing valve valving member, and wherein the position of the flow sharing valve valving member controllably varies a fluid communication between the second high pressure output and the adder port.

4. The switching system of claim 3, wherein the means for controlling the pressurization of the second pump includes a pressure regulating valve having a first port coupled to the second pump bypass, a second port coupled to the second high pressure output, and a pressure regulating valve valving member movably positioned to controllably vary a fluid communication between the second high pressure output and the second pump bypass, the flow sharing valve further including a fourth port coupled to the high pressure supply and a fifth port, and wherein the position of the flow sharing valve valving member controllably varies a fluid communication between the fourth port and the fifth port, the pressure regulating valve having a control port coupled to the fifth port of the flow sharing valve, and wherein the position of the pressure regulating valve valving member is controlled by a pressure communicated by the control port.

5. The switching system of claim 4, wherein a reduction in pressure at the sensing port causes movement of the sensing valve valving member such that the position port is coupled to the pressure reduction port, which causes movement of the flow sharing valve valving member such that the fourth port is coupled to the fifth port, which causes movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass decreases whereby a pressure in the second high pressure output increases.

6. The switching system of claim 5, wherein a continuing reduction in pressure at the sensing port results in further movement of the flow sharing valve valving member such that the second high pressure output is coupled to the adder port thereby adding flow from the second pump to the high pressure supply to the fuel metering unit.

7. The switching system of claim 4, wherein an increase in pressure at the sensing port causes movement of the sensing valve valving member such that the position port is coupled to the pressure addition port, which causes movement of the flow sharing valve valving member such that the adder port is at least partially closed from the second high pressure output thereby subtracting flow from the second pump to the high pressure supply to the fuel metering unit.

8. The switching system of claim 7, wherein a continuing increase in pressure at the sensing port results in further movement of the flow sharing valve valving member such the fourth port is at least partially closed from the fifth port, which causes movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass is increased whereby a pressure in the second high pressure output decreases.

9. The switching system of claim 2, wherein the means for adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump includes an adder valve having a first port coupled to the second high pressure output of the second pump, an adder port coupled to the high pressure supply to the fuel metering unit, and a adder valving member positioned between the first port and the adder port that is spring biased to a closed position, and wherein a differential pressure between the first port and the adder port controls a position of the adder valve valving member, and wherein the position of the adder valve valving member controllably varies a fluid communication between the second high pressure output and the adder port.

10. The switching system of claim 9, wherein the means for controlling the pressurization of the second pump includes a pressure regulating valve having a first port coupled to the second pump bypass, a second port coupled to the second high pressure output, and a pressure regulating valve valving member movably positioned to controllably vary a fluid communication between the second high pressure output and the second pump bypass, the flow sharing valve further including a control port coupled to the positioning port of the sensing valve, and wherein the position of the pressure regulating valve valving member is controlled by a pressure communicated by the control port.

11. The switching system of claim 10, wherein a reduction in pressure at the sensing port causes movement of the sensing valve valving member such that the positioning port is coupled to the pressure addition port, which causes movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass decreases whereby a pressure in the second high pressure output increases.

12. The switching system of claim 11, wherein a continuing reduction in pressure at the sensing port results in further increase in pressure in the second high pressure output creating a pressure differential across the adder valve valving member causing movement thereof such that the second high pressure output is coupled to the adder port thereby adding flow from the second pump to the high pressure supply to the fuel metering unit.

13. The switching system of claim 4, wherein an increase in pressure at the sensing port causes movement of the sensing valve valving member such that the positioning port is coupled to the pressure reduction port, which causes movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass is increased whereby a pressure in the second high pressure output decreases thereby reducing the pressure differential across the adder valve valving member and reducing flow from the second pump to the high pressure supply to the fuel metering unit.

14. The switching system of claim 13, wherein a continuing increase in pressure at the sensing port results in further movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass is increased whereby a pressure in the second high pressure output decreases thereby further decreasing the pressure differential across the adder valve valving member resulting is closure thereof and elimination of flow from the second pump to the high pressure supply to the fuel metering unit.

15. The switching system of claim 1, wherein the means for sensing the bypass flow from the fuel metering unit and the means for adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump include a flow sharing valve having a sensing port coupled to a bypass return from the fuel metering unit, a return port coupled to the low pressure return, and a flow sharing valve valving member positioned therebetween, the flow sharing valve further including a position port and a pressure addition port, wherein a differential pressure between the sensing port and the return port controls a position of the sensing valve valving member, and wherein the position of the sensing valve valving member selectively couples the pressure addition port to the position port, the flow sharing valve further having a first port coupled to the second high pressure output of the second pump and an adder port coupled to high pressure supply to the fuel metering unit, and wherein the position of the flow sharing valve valving member controllably varies a fluid communication between the second high pressure output and the adder port.

16. The switching system of claim 15, wherein the means for controlling the pressurization of the second pump includes a pressure regulating valve having a first port coupled to the second pump bypass, a second port coupled to the second high pressure output, a control port coupled to the position port of the flow sharing valve, a pressure reduction port coupled to the second pump bypass, and a pressure regulating valve valving member movably positioned to controllably vary a fluid communication between the second high pressure output and the second pump bypass, and wherein the position of the pressure regulating valve valving member is controlled by at least one of a pressure communicated by the control port and by the pressure reduction port.

17. The switching system of claim 16, wherein a reduction in pressure at the sensing port causes movement of the flow sharing valve valving member such that the positioning port is coupled to the pressure addition port, which causes movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass decreases whereby a pressure in the second high pressure output increases.

18. The switching system of claim 17, wherein a continuing reduction in pressure at the sensing port results in further movement of the flow sharing valve valving member such that the second high pressure output is coupled to the adder port thereby adding flow from the second pump to the high pressure supply to the fuel metering unit.

19. The switching system of claim 18, wherein an increase in pressure at the sensing port causes movement of the flow sharing valve valving member such that the adder port is at least partially closed from the second high pressure output thereby subtracting flow from the second pump to the high pressure supply to the fuel metering unit.

20. The switching system of claim 19, wherein a continuing increase in pressure at the sensing port causes further movement of the flow sharing valve valving member such that the position port is decoupled from the pressure addition port such that a reduction in pressure on the pressure regulating valve via the pressure reduction port results in movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass is increased whereby a pressure in the second high pressure output decreases.

21. The switching system of claim 1, wherein the means for sensing the bypass flow from the fuel metering unit and the means for controlling the pressurization of the second pump to the first high pressure output from the first pump include a pressure regulating valve having a sensing port coupled to a bypass return from the fuel metering unit, a pressure reduction port coupled to the second pump bypass, and a pressure regulating valve valving member positioned therebetween, the pressure regulating valve further including a first port coupled to the second pump bypass, a second port coupled to the second high pressure output, a third port in fluid communication with the second port, and wherein the pressure regulating valve valving member is movably positioned to controllably vary a fluid communication between the second high pressure output and the second pump bypass, and wherein the position of the pressure regulating valve valving member is controlled by a pressure differential between the sensing port and the pressure reduction port.

22. The switching system of claim 21, wherein the means for adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump includes an adder valve having a first port coupled to the third port of the pressure regulating valve, an adder port coupled to the high pressure supply to the fuel metering unit, and a adder valve valving member positioned between the first port and the adder port that is spring biased to a closed position, and wherein a differential pressure between the first port and the adder port controls a position of the adder valve valving member, and wherein the position of the adder valve valving member controllably varies a fluid communication between the second high pressure output and the adder port.

23. The switching system of claim 22, wherein a reduction in pressure at the sensing port causes movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass decreases whereby a pressure in the second high pressure output increases.

24. The switching system of claim 23, wherein a continuing reduction in pressure at the sensing port results in further increase in pressure in the second high pressure output creating a pressure differential across the adder valve valving member causing movement thereof such that the second high pressure output is coupled to the adder port thereby adding flow from the second pump to the high pressure supply to the fuel metering unit.

25. The switching system of claim 24, wherein an increase in pressure at the sensing port causes movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass is increased whereby a pressure in the second high pressure output decreases thereby reducing the pressure differential across the adder valve valving member and reducing flow from the second pump to the high pressure supply to the fuel metering unit.

26. The switching system of claim 25, wherein a continuing increase in pressure at the sensing port results in further movement of the pressure regulating valve valving member whereby fluid communication between the second high pressure output and the second pump bypass is increased whereby a pressure in the second high pressure output decreases thereby further decreasing the pressure differential across the adder valve valving member resulting is closure thereof and elimination of flow from the second pump to the high pressure supply to the fuel metering unit.

27. The switching system of claim 1, wherein the means for sensing the bypass flow from the fuel metering unit, the means for controlling the pressurization of the second pump to the first high pressure output from the first pump, and the means for adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump include a flow sharing valve having a sensing port coupled to a bypass return from the fuel metering unit, a pressure reduction port coupled to the second pump bypass, and a flow sharing valve valving member positioned therebetween, the flow sharing valve further including a first port coupled to the second pump bypass, a second port coupled to the second high pressure output, a third port coupled to the high pressure supply to the fuel metering unit, and wherein the flow sharing valve valving member is movably positioned to controllably vary a fluid communication between the second high pressure output, the second pump bypass, and the high pressure supply, and wherein the position of the flow sharing valve valving member is controlled by a pressure differential between the sensing port and the pressure reduction port.

28. The switching system of claim 27, wherein a reduction in pressure at the sensing port causes movement of the flow sharing valve valving member whereby fluid communication between the second high pressure output and the second pump bypass decreases whereby a pressure in the second high pressure output increases, and whereby fluid communication between the second high pressure output and the high pressure supply increases thereby adding flow from the second pump to the high pressure supply to the fuel metering unit.

29. The switching system of claim 28, wherein an increase in pressure at the sensing port causes movement of the flow sharing valve valving member whereby fluid communication between the second high pressure output and the second pump bypass is increased whereby a pressure in the second high pressure output decreases, and whereby fluid communication between the second high pressure output and the high pressure supply decreases thereby reducing flow from the second pump to the high pressure supply to the fuel metering unit.

30. A method of switching a dual pump fuel supply system for an aircraft engine, the dual pump fuel supply system including a first pump having a first high pressure output coupled to a high pressure supply to a fuel metering unit, wherein the fuel metering unit is configured to supply a portion of the fuel supply to an engine and to return a bypass flow of the fuel supply to a low pressure return that is coupled to a first low pressure supply to the first pump, and a second pump having a second high pressure output and a second low pressure supply that is coupled to the low pressure return, the second pump also having a second pump bypass that is coupled to the second low pressure supply, comprising the steps of:

sensing the bypass flow coming directly from the fuel metering unit;

controlling a pressurization of the second pump based on the step of sensing; and

adding or subtracting the second high pressure output from the second pump to the first high pressure output from the first pump and providing an output flow to the downstream fuel metering unit based on the step of controlling.